Experimental Study And Mechanism Analysis On Particle Spray Agglomeration From Coal Combustion

Submicrometer paticles are main pollutants to atmosphere in China currently. It has caught worldwide attention to control submicrometer particles effectively. Although the efficiency of existing equipment(such as EPS, bag house) can reach so much as 99%, a mass of submicrometer particles are emitted into atmosphere. The submicron particles can be agglomerated and absorbed through physical and chemical effects by agglomerant solution which was sprayed into the flue before the precipitator. Then the aggregates can be caught effectively by existing equipment. This novel pre-agglomerate technology needn't change the operating conditions of existing equipment. Also this method can remove multi-pollutants simultaneously. It may become the tendency of deep de-dust technology.On the basis of previous researches, we proposed a new style complex spouted fluidized technique. Systematic experiments and theoretical studies has been done in this paper which can provide theoretical and technical supports for controlling submicron particles effectively.An experiment platform of spray agglomeration has been designed and built. Systematic experiments were conducted in multistage spouted tower using some different kinds of agglomerants. Results show that the afterbody dust concentration descends effectively after spraying agglomerants. The influencing factors including surfactant, pH value, flow rate, concentration and the storage time of agglomerant solutions were analyzed. In addition, the influence of temperature, particle concentration in the simulated flue gas and the gas quantity were also discussed. The effects of compound agglomerants and modifying Ca-contained materials were discussed in the paper. Microstructure characteristics of aggregates were analysed using SEM. Final results indicate that small particles increase obviously and it is more compact between large scale particles.Aggregates from different zone of the tower show different microstructrue characteristics. In the first-class tower, the agglomerate behavior is of priority with being enwrapped and adhered by agglomerants. In the second-class tower, the behavior is prior to absorption and solidification by the aqueous particles. Ca-contained materials and different desulfurization technics all show the ability of removing particles from coal combustion.Flocculation and hard-agglomeration theories are presented to explain the agglomeration mechanism of partiles in the spay process. The ways to promote the agglomeration are introduced. Factors that might influence the effect of agglomeration are discussed. A model of submicro agglomeration during the spray process was developed combining swiftness-flocculation theory and analysis of the interaction of droplets and particulates. Basing on the model, settling rate and the influences of original parameters were caculated.